Dark Duck Duck Go!

Looks great, almost like Edge or a UWP app. It's really clean. The contrast of this theme is on the low end. Whether this is a good or bad thing comes down to personal preference. I see the appeal of keeping the URL bar and UI buttons a little faint, so you can better focus on the web content you're accessing. But for me, I kinda like having a high contrast UI, it is more practical for quick operations, I think. If it's too hi-contrast or too dark it becomes agitating or moody for me. This theme has a balanced approach to the many dark theme challenges.